Electrical purification apparatus

ABSTRACT

An electrical purification apparatus and methods of making same are disclosed. The electrical purification apparatus may provide for increases in operation efficiencies, for example, with respect to current efficiencies and membrane utilization.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) of U.S.Provisional Patent Application Ser. No. 61/413,021, filed on Nov. 12,2010, titled “CROSS-FLOW ELECTROCHEMICAL DEIONIZATION DEVICE AND METHODSOF MANUFACTURING THEREOF” and U.S. Provisional Patent Application Ser.No. 61/510,157, filed on Jul. 21, 2011, titled “MODULAR CROSS-FLOWELECTRODIALYSIS DEVICES AND METHODS OF MANUFACTURING THEREOF,” theentire disclosure of each of which is hereby incorporated herein byreference in its entirety for all purposes.

FIELD OF THE DISCLOSURE

This disclosure relates to systems and methods of water treatment, andmethods of making a system or apparatus for treating water. Moreparticularly, this disclosure relates to systems and methods of watertreatment using an electrical purification apparatus, and methods ofmaking an electrical purification apparatus for treating water.

SUMMARY

One or more aspects of the disclosure relate to a method of preparing afirst cell stack for an electrical purification apparatus. The methodmay comprise securing a first anion exchange membrane to a first cationexchange membrane at a first portion of a periphery of the first anionexchange membrane and the first cation exchange membrane to form a firstcompartment having a first fluid flow path. The method may also comprisesecuring a second anion exchange membrane to the first cation exchangemembrane at a second portion of the periphery of the first cationexchange membrane and a first portion of a periphery of the second anionexchange membrane to form a second compartment having a second fluidflow path in a direction different from the first fluid flow path. Eachof the first compartment and the second compartment may be constructedand arranged to provide a fluid contact of greater than 85% of thesurface area of each of the first cation exchange membrane, the firstanion exchange membrane and the second cation exchange membrane.

Other aspects of the disclosure relate to a method for preparing a cellstack for an electrical purification apparatus. The method may compriseforming a first compartment by securing a first cation exchange membraneto a first anion exchange membrane at a first portion of a periphery ofthe first cation exchange membrane and the first anion exchange membraneto provide a first spacer assembly having a first spacer disposedbetween the first cation exchange membrane and the first anion exchangemembrane. The method may also comprise forming a second compartment bysecuring a second anion exchange membrane to a second cation exchangemembrane at a first portion of a periphery of the second cation exchangemembrane and the second anion exchange membrane to provide a secondspacer assembly having a second spacer disposed between the second anionexchange membrane and the second cation exchange membrane. The methodmay also comprise forming a third compartment by securing the firstspacer assembly to the second spacer assembly at a second portion of theperiphery of the first cation exchange membrane and at a portion of theperiphery of the second anion exchange membrane to provide a stackassembly having a spacer disposed between the first spacer assembly andthe second spacer assembly. Each of the first compartment and the secondcompartment may be constructed and arranged to provide a direction offluid flow in a direction different from the direction of fluid flow inthe third compartment.

Still other aspects of the disclosure may provide an electricalpurification apparatus comprising a cell stack. The cell stack maycomprise a first compartment comprising a first cation exchange membraneand a first anion exchange membrane. The first compartment may beconstructed and arranged to provide a direct fluid flow in a firstdirection between the first cation exchange membrane and the first anionexchange membrane. The cell stack may also comprise a second compartmentcomprising the first anion exchange membrane and a second cationexchange membrane to provide a direct fluid flow in a second directionbetween the first anion exchange membrane and the second cation exchangemembrane. Each of the first compartment and the second compartmentconstructed and arranged to provide a fluid contact of greater than 85%of the surface area of the first cation exchange membrane, the firstanion exchange membrane, and the second cation exchange membrane.

Still other aspects of the disclosure relate to a cell stack for anelectrical purification apparatus. The cell stack may comprise aplurality of alternating ion depleting and ion concentratingcompartments. Each of the ion depleting compartments may have an inletand an outlet that provides a dilute fluid flow in a first direction.Each of the ion concentrating compartments may have an inlet and anoutlet that provides a concentrated fluid flow in a second directionthat is different from the first direction. The cell stack may alsocomprise a blocking spacer positioned in the cell stack. The blockingspacer may be constructed and arranged to alter the direction of atleast one of a dilute fluid flow and a concentrated fluid flow throughthe cell stack.

Still other aspects of the disclosure relate to an electricalpurification apparatus. The electrical purification apparatus comprisesa cell stack comprising alternating ion diluting compartments and ionconcentrating compartments. Each of the ion diluting compartments may beconstructed and arranged to provide a fluid flow in a first direction.Each of the ion concentrating compartments may be constructed andarranged to provide a fluid flow in a second direction that is differentfrom the first direction. The electrical purification apparatus maycomprise a first electrode adjacent an anion exchange membrane at afirst end of the cell stack. The electrical purification apparatus mayalso comprise a second electrode adjacent a cathode exchange membrane ata second end of the cell stack. A blocking spacer may be positioned inthe cell stack and constructed and arranged to redirect at least one ofa dilute fluid flow and a concentrate fluid flow through the electricalpurification apparatus and to prevent a direct current path between thefirst electrode and the second electrode.

In still further aspects of the disclosure, a method of providing asource of potable water is provided. The method may comprise providingan electrical purification apparatus comprising a cell stack. The cellstack may comprise alternating ion diluting compartments and ionconcentrating compartments. Each of the ion diluting compartments may beconstructed and arranged to provide a fluid flow in a first direction.Each of the ion concentrating compartments may be constructed andarranged to provide a fluid flow in a second direction that is differentfrom the first direction. Each of the ion concentrating compartments andion diluting compartments may be constructed and arranged to provide afluid contact of greater than 85% of the surface area of each of thealternating ion diluting compartments and ion depleting compartments.The method may further comprise fluidly connecting a seawater feedstream comprising about 35,000 ppm total dissolved solids to an inlet ofthe electrical purification apparatus. The method may further comprisefluidly connecting an outlet of the electrical purification apparatus toa potable point of use.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various FIGs. is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing.

In the Drawings:

FIG. 1 is a schematic illustration of a portion of an electricalpurification apparatus in accordance with one or more embodiments of thedisclosure;

FIG. 2 is a schematic illustration of a portion of an electricalpurification apparatus in accordance with one or inure embodiments ofthe disclosure;

FIG. 3 is a schematic illustration of a portion of an electricalpurification apparatus in accordance with one or more embodiments of thedisclosure;

FIG. 4 is a schematic illustration of a portion of an electricalpurification apparatus in accordance with one or more embodiments of thedisclosure;

FIG. 5 is a schematic illustration of a side view of a portion of anelectrodeionization apparatus comprising a membrane cell stackpositioned in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 6 is a schematic illustration of a side view of a portion of anelectrodeionization apparatus comprising a membrane cell stackpositioned in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 7 is a schematic illustration of a side view of a portion of anelectrodeionization apparatus comprising a membrane cell stackpositioned in a housing in accordance with one or inure embodiments ofthe disclosure;

FIG. 8 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or inure embodiments ofthe disclosure;

FIG. 9 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 10 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 11 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 12 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 13 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 14 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 15 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 16 is a schematic illustration of a method of securing a membranecell stack in a housing in accordance with one or more embodiments ofthe disclosure;

FIG. 17 is a schematic illustration of a multiple-pass electricalpurification apparatus in accordance with one or more embodiments of thedisclosure;

FIG. 18 is a schematic illustration of a blocking spacer in accordancewith one or more embodiments of the disclosure;

FIG. 19 is a schematic illustration of spacer assemblies and a blockingspacer positioned therebetween in accordance with one or moreembodiments of the disclosure;

FIG. 20 is a schematic illustration of a portion of an electricalpurification apparatus comprising a cell stack positioned in a housingin accordance with one or more embodiments of the disclosure;

FIG. 21 is a schematic illustration of a blocking spacer in accordancewith one or more embodiments of the disclosure;

FIG. 22 is a schematic illustration of a portion of an electricalpurification apparatus comprising a cell stack positioned in a housingin accordance with one or more embodiments of the disclosure;

FIGS. 23A and 23B are schematic illustrations of a portion of anelectrical purification apparatus comprising a cell stack positioned ina housing in accordance with one or more embodiments of the disclosure;

FIGS. 24A and 24B are schematic illustrations of a portion of anelectrical purification apparatus comprising a first modular unit, asecond modular unit, and a blocking spacer positioned therebetween inaccordance with one or more embodiments of the disclosure;

FIG. 25 is a schematic illustration of a blocking spacer in accordancewith one or more embodiments of the disclosure;

FIG. 26 is a schematic illustration of a spacer assembly in accordancewith one or more embodiments of the disclosure;

FIG. 27 is a schematic illustration of a cell stack in accordance withone or more embodiments of the disclosure;

FIG. 28 is a schematic illustration of a cell stack in accordance withone or more embodiments of the disclosure;

FIG. 29 is a schematic illustration of a cell stack in accordance withone or more embodiments of the disclosure;

FIG. 30 is a schematic illustration of a spacer in accordance with oneor more embodiments of the disclosure;

FIG. 31 is a schematic illustration of an exploded view and through ofcell stack of spacers and membranes in accordance with one or moreembodiments of the disclosure;

FIG. 32 is a schematic illustration of a cross-section view and detailedview of a partially assembled cell stack in accordance with one or moreembodiments of the disclosure;

FIG. 33 is a schematic illustration of part of an assembled stack inaccordance with one or more embodiments of the disclosure;

FIG. 34 is a schematic illustration of an overmolded spacer inaccordance with one or more embodiments of the disclosure;

FIG. 35 is a schematic illustration of a section view of a cell stack inaccordance with one or more embodiments of the disclosure;

FIG. 36 is schematic illustration of a section view of a cell stack inaccordance with one or more embodiments of the disclosure;

FIG. 37 is a schematic illustration of a top view of a spacer inaccordance with one or more embodiments of the disclosure;

FIGS. 38A and 38B are schematic illustrations of a detail of a spacer inaccordance with one or more embodiments of the disclosure. FIG. 38B is across-section of FIG. 38A along line B-B.

FIG. 39 is a schematic illustration of a stack of spacers and membranesin accordance with one or more embodiments of the invention;

FIG. 40 is a schematic illustration of a stack of spacers and membranesin accordance with one or more embodiments of the invention;

FIG. 41 is a schematic illustration of a stack of spacers and membranesin accordance with one or more embodiments of the invention;

FIG. 42 is a schematic illustration of a stack of spacers and membranesin accordance with one or more embodiments of the invention;

FIG. 43 is a schematic illustration of a stack of spacers and membranesin accordance with one or more embodiments of the invention; and

FIG. 44 is a schematic illustration of a stack of spacers and membranesin accordance with one or more embodiments of the invention

At least some of the drawings may depict membranes, spacers, cellstacks, and housings in particular configurations and geometries.However, the disclosure is not limited to these particularconfigurations and geometries. For example, the housing may be of anysuitable geometry such that one or more membrane cell stacks or modularunits may be secured within. For example, the housing may becylindrical, polygonal, square, or rectangular. With regard to themembrane cell stacks and modular units, any suitable geometry isacceptable so long as the cell stack or modular unit may be secured tothe housing. For example the membranes or spacers may be rectangular inshape. In certain embodiments, a housing may not be required. Thegeometry of the membranes and spacers may be of any suitable geometrysuch that the membranes and spacers may be secured within a cell stack.In certain embodiments, a particular number of corners or vertices onthe cell stack may be desired. For example, three or more corners orvertices may be desired to secure the cell stack to the housing. Incertain embodiments, the geometry of any of the housing, cell stack,membranes, and spacers may selected to accommodate operationalparameters of the electrical purification apparatus. For example, thespacers may be asymmetrical to accommodate differences in flow ratesbetween the dilute and concentrate streams.

DETAILED DESCRIPTION

Devices for purifying fluids using electrical fields are commonly usedto treat water and other liquids containing dissolved ionic species. Twotypes of devices that treat water in this way are electrodeionizationand electrodialysis devices.

Electrodeionization (EDI) is a process that removes, or at leastreduces, one or more ionized or ionizable species from water usingelectrically active media and an electric potential to influence iontransport. The electrically active media typically serves to alternatelycollect and discharge ionic and/or ionizable species and, in some cases,to facilitate the transport of ions, which may be continuously, by ionicor electronic substitution mechanisms. EDI devices can compriseelectrochemically active media of permanent or temporary charge, and maybe operated batch-wise, intermittently, continuously, and/or even inreversing polarity modes. EDT devices may be operated to promote one ormore electrochemical reactions specifically designed to achieve orenhance performance. Further, such electrochemical devices may compriseelectrically active membranes, such as semi-permeable or selectivelypermeable ion exchange or bipolar membranes. Continuouselectrodeionization (CEDI) devices are EDI devices known to thoseskilled in the art that operate in a manner in which water purificationcan proceed continuously, while ion exchange material is continuouslyrecharged. CEDI techniques can include processes such as continuousdeionization, filled cell electrodialysis, or electrodiaresis. Undercontrolled voltage and salinity conditions, in CEDI systems, watermolecules can be split to generate hydrogen or hydronium ions or speciesand hydroxide or hydroxyl ions or species that can regenerate ionexchange media in the device and thus facilitate the release of thetrapped species therefrom. In this manner, a water stream to be treatedcan be continuously purified without requiring chemical recharging ofion exchange resin.

Electrodialysis (ED) devices operate on a similar principle as CEDI,except that ED devices typically do not contain electroactive mediabetween the membranes. Because of the lack of electroactive media, theoperation of ED may be hindered on feed waters of low salinity becauseof elevated electrical resistance. Also, because the operation of ED onhigh salinity feed waters can result in elevated electrical currentconsumption, ED apparatus have heretofore been most effectively used onsource waters of intermediate salinity. In ED based systems, becausethere is no electroactive media, splitting water is inefficient andoperating in such a regime is generally avoided.

In CEDI and ED devices, a plurality of adjacent cells or compartmentsare typically separated by selectively permeable membranes that allowthe passage of either positively or negatively charged species, buttypically not both. Dilution or depletion compartments are typicallyinterspaced with concentrating or concentration compartments in suchdevices. As water flows through the depletion compartments, ionic andother charged species are typically drawn into concentratingcompartments under the influence of an electric field, such as a DCfield. Positively charged species are drawn toward a cathode, typicallylocated at one end of a stack of multiple depletion and concentrationcompartments, and negatively charged species are likewise drawn towardan anode of such devices, typically located at the opposite end of thestack of compartments. The electrodes are typically housed inelectrolyte compartments that are usually partially isolated from fluidcommunication with the depletion and/or concentration compartments. Oncein a concentration compartment, charged species are typically trapped bya barrier of selectively permeable membrane at least partially definingthe concentration compartment. For example, anions are typicallyprevented from migrating further toward the cathode, out of theconcentration compartment, by a cation selective membrane. Once capturedin the concentrating compartment, trapped charged species can be removedin a concentrate stream.

In CEDI and ED devices, the DC field is typically applied to the cellsfrom a source of voltage and electric current applied to the electrodes(anode or positive electrode, and cathode or negative electrode). Thevoltage and current source (collectively “power supply”) can be itselfpowered by a variety of means such as an AC power source, or forexample, a power source derived from solar, wind, or wave power. At theelectrode/liquid interfaces, electrochemical half cell reactions occurthat initiate and/or facilitate the transfer of ions through themembranes and compartments. The specific electrochemical reactions thatoccur at the electrode/interfaces can be controlled to some extent bythe concentration of salts in the specialized compartments that housethe electrode assemblies. For example, a feed to the anode electrolytecompartments that is high in sodium chloride will tend to generatechlorine gas and hydrogen ion, while such a feed to the cathodeelectrolyte compartment will tend to generate hydrogen gas and hydroxideion. Generally, the hydrogen ion generated at the anode compartment willassociate with a free anion, such as chloride ion, to preserve chargeneutrality and create hydrochloric acid solution, and analogously, thehydroxide ion generated at the cathode compartment will associate with afree cation, such as sodium, to preserve charge neutrality and createsodium hydroxide solution. The reaction products of the electrodecompartments, such as generated chlorine gas and sodium hydroxide, canbe utilized in the process as needed for disinfection purposes, formembrane cleaning and defouling purposes, and for pH adjustmentpurposes.

Plate-and-frame and spiral wound designs have been used for varioustypes of electrochemical deionization devices including but not limitedto electrodialysis (ED) and electrodeionization (EDI) devices.Commercially available ED devices are typically of plate-and-framedesign, while EDI devices are available in both plate and frame andspiral configurations.

The present invention relates to devices that may purify fluidselectrically that may be contained within a housing, as well as methodsof manufacture and use thereof. Liquids or other fluids to be purifiedenter the purification device or apparatus and, under the influence ofan electric field, are treated to produce an ion-depleted liquid.Species from the entering liquids are collected to produce anion-concentrated liquid. The components of the electrical purificationapparatus, which may also be referred to as an electrochemicalseparation system or an electrochemical separation device, may beassembled using various techniques to achieve optimal operation of theapparatus.

In some embodiments of the present disclosure, a method is provided forsecuring or bonding ion exchange membranes and, optionally, spacers toproduce a membrane cell stack for an electrical purification apparatus.The method may provide for securing of multiple anion exchange membranesand cation exchange membranes for use in electrical purificationapparatus such as a cross-flow electrodialysis (ED) device.

In certain embodiments of the disclosure, a method of preparing a firstcell stack for an electrical purification apparatus is provided. Themethod may comprise securing a first ion exchange membrane to a secondion exchange membrane. A spacer may be positioned between the first ionexchange membrane and the second ion exchange membrane to form a spacerassembly. When used in an electrical purification apparatus, this spacerassembly defines a first compartment that may allow fluid flow. Aplurality of ion exchange membranes may be secured to one another toprovide a series of compartments. In certain embodiments, a plurality ofspacer assemblies may be constructed and the spacer assemblies may besecured to one another. A spacer may be positioned between each of thespacer assemblies. In this way, a series of compartments for anelectrical purification apparatus is constructed to allow fluid flow inone or more directions in each of the compartments.

The spacers that may be positioned within the compartments may providestructure to and define the compartments and, in certain examples, mayassist in directing fluid flow through the compartment. The spacers maybe made of polymeric materials or other materials that allow for adesired structure and fluid flow within the compartments. In certainembodiments, the spacers may be constructed and arranged to redirect orredistribute fluid flow within the compartments. In some examples, thespacer may comprise a mesh-like or screen material to provide structureand allow for the desired fluid flow through the compartment.

In accordance with one or more embodiments, the efficiency ofelectrochemical separation systems may be improved. Current loss is onepotential source of inefficiency. In some embodiments, such as thoseinvolving a cross-flow design, the potential for current leakage may beaddressed. Current efficiency may be defined as the percentage ofcurrent that is effective in moving ions out of the dilute stream intothe concentrate stream. Various sources of current inefficiency mayexist in an electrochemical separation system or electrical purificationapparatus. One potential source of inefficiency may involve current thatbypasses the cell pairs (pairs of adjacent concentration and dilutingcompartments) by flowing through the dilute and concentrate inlet andoutlet manifolds. Open inlet and outlet manifolds may be in direct fluidcommunication with flow compartments and may reduce pressure drop ineach flow path. Part of the electrical current from one electrode to theother may bypass the stack of cell pairs by flowing through the openareas. The bypass current reduces current efficiency and increasesenergy consumption. Another potential source of inefficiency may involveions that enter the dilute stream from the concentrate due to imperfectpermselectivity of ion exchange membranes. In some embodiments,techniques associated with the sealing and potting of membranes andscreens within a device may facilitate reduction of current leakage.

In one or more embodiments, a bypass path through a stack may bemanipulated to promote current flow along a direct path through a cellstack so as to improve current efficiency. In some embodiments, anelectrochemical separation device or electrical purification apparatusmay be constructed and arranged such that one or more bypass paths aremore tortuous than a direct path through the cell stack. In at leastcertain embodiments, an electrochemical separation device or electricalpurification apparatus may be constructed and arranged such that one ormore bypass paths present higher resistance than a direct path throughthe cell stack. In some embodiments involving a modular system,individual modular units may be configured to promote currentefficiency. Modular units may be constructed and arranged to provide acurrent bypass path that will contribute to current efficiency. Innon-limiting embodiments, a modular unit may include a manifold systemand/or a flow distribution system configured to promote currentefficiency. In at least some embodiments, a frame surrounding a cellstack in an electrochemical separation unit may be constructed andarranged to provide a predetermined current bypass path. In someembodiments, promoting a multi-pass flow configuration within anelectrochemical separation device may facilitate reduction of currentleakage. In at least some non-limiting embodiments, blocking membranesor spacers may be inserted between modular units to direct dilute and/orconcentrate streams into multiple-pass flow configurations for improvedcurrent efficiency. In some embodiments, current efficiency of at leastabout 60% may be achieved. In other embodiments, a current efficiency ofat least about 70% may be achieved. In still other embodiments, acurrent efficiency of at least about 80% may be achieved. In at leastsome embodiments, a current efficiency of at least about 85% may beachieved.

The spacer may be constructed and arranged to redirect at least one offluid flow and electrical current to improve current efficiency. Thespacer may also be constructed and arranged to create multiple fluidflow stages in an electrical purification apparatus. The spacer maycomprise a solid portion to redirect fluid flow in a particulardirection. The solid portion may also redirect electrical current flowin a particular direction, and prevent a direct path between an anodeand a cathode in an electrical purification apparatus. A spacercomprising a solid portion may be referred to as a blocking spacer. Theblocking spacer may be positioned within a cell stack, or may bepositioned between a first cell stack, or first modular unit, and asecond cell stack, or second modular unit.

In some embodiments, the plurality of ion exchange membranes secured toone another may alternate between cation exchange membranes and anionexchange membranes to provide a series of ion diluting compartments andion concentrating compartments.

The geometry of the membranes may be of any suitable geometry such thatthe membranes may be secured within a cell stack. In certainembodiments, a particular number of corners or vertices on the cellstack may be desired so as to suitably secure the cell stack within ahousing. In certain embodiments, particular membranes may have differentgeometries than other membranes in the cell stack. The geometries of themembranes may be selected to assist in at least one of securing themembranes to one another, to secure spacers within the cell stack, tosecure membranes within a modular unit, to secure membranes within asupport structure, to secure a group of membranes such as a cell stackto a housing, and to secure a modular unit into a housing.

The membranes, spacers, and spacer assemblies may be secured at aportion of a periphery or edge of the membranes, spacers, or spacerassemblies. A portion of a periphery may be a continuous ornon-continuous length of the membrane, spacer, or spacer assembly. Theportion of the periphery that is selected to secure the membrane,spacer, or spacer assembly may provide a boundary or border to directfluid flow in a predetermined direction.

In certain embodiments, a method of preparing a cell stack may comprisesecuring a first anion exchange membrane to a first cation exchangemembrane at a first portion of a periphery of the first anion exchangemembrane and the first cation exchange membrane to form a firstcompartment having a first fluid flow path. The method may furthercomprise securing a second anion exchange membrane to the first cationexchange membrane at a second portion of the periphery of the firstcation exchange membrane and a first portion of a periphery of thesecond anion exchange membrane to form a second compartment having asecond fluid flow path in a direction different from the first fluidflow path.

The first fluid flow path and the second fluid flow path may be selectedand provided by way of the portions of the peripheries of the ionexchange membranes that are secured to one another. Using the firstfluid flow path as a direction running along a 0° axis, the second fluidflow path may run in a direction of any angle greater than zero degreesand less than 360°. In certain embodiments of the disclosure, the secondfluid flow path may run at a 90° angle, or perpendicular to the firstfluid flow path. In other embodiments, the second fluid flow path mayrun at a 180° angle to the first fluid flow path. In another embodiment,the first fluid flow path may be running in a direction of 0°. Thesecond fluid flow path may be running at 60°, and a third fluid flowpath may be running at 120°. A fourth fluid flow path may be running at0°.

If additional ion exchange membranes are secured to the cell stack toprovide additional compartments, the fluid flow paths in theseadditional compartments may be the same or different from the firstfluid flow path and the second fluid flow path. In certain embodiments,the fluid flow path in each of the compartments alternates between afirst fluid flow path and a second fluid flow path. For example, thefirst fluid flow path in the first compartment may be running in adirection of 0°. The second fluid flow path in the second compartmentmay be running in a direction of 90°, and the third fluid flow path inthe third compartment may be running in a direction of 0°. In certainexamples, a first fluid flow path running in a first direction, and asecond fluid flow path running in a second direction may be referred toas cross-flow electrical purification.

In other embodiments, the fluid flow path in each of the compartmentsalternates sequentially between a first fluid flow path, a second fluidflow path, and a third fluid flow path. For example, the first fluidflow path in the first compartment may be running in a direction of 0°.The second fluid flow path in the second compartment may be running at30°, and the third fluid flow path in the third compartment may berunning at 90°. The fourth fluid flow path in the fourth compartment maybe running at 0°. In another embodiment, the first fluid flow path inthe first compartment may be running in a direction of 0°. The secondfluid flow path in the second compartment may be running at 60°, and thethird fluid flow path in the third compartment may be running at 120°.The fourth fluid flow path in the fourth compartment may be running at0°.

In certain embodiments of the disclosure, the flow within a compartmentmay be adjusted, redistributed, or redirected to provide greater contactof the fluid with the membrane surfaces within the compartment. Thecompartment may be constructed and arranged to redistribute fluid flowwithin the compartment. The compartment may have obstructions,projections, protrusions, flanges, or baffles that may provide astructure to redistribute the flow through the compartment, which willbe discussed further below. In certain embodiments, the obstructions,projections, protrusions flanges, or baffles may be referred to as aflow redistributor.

Each of the compartments in the cell stack for an electricalpurification apparatus may be constructed and arranged to provide apredetermined percentage of surface area or membrane utilization forfluid contact. It has been found that greater membrane utilizationprovides greater efficiencies in the operation of the electricalpurification apparatus. Advantages of achieving greater membraneutilization may include lower energy consumption, smaller footprint ofthe apparatus, less passes through the apparatus, and higher qualityproduct water. In certain embodiments, the membrane utilization that maybe achieved is greater than 65%. In other embodiments, the membraneutilization that may be achieved is greater than 75%. In certain otherembodiments, the membrane utilization that may be achieved may begreater than 85%. The membrane utilization may be at least in partdependent on the methods used to secure each of the membranes to oneanother, and the design of the spacer. In order to obtain apredetermined membrane utilization, appropriate securing techniques andcomponents may be selected in order to achieve a reliable and secureseal that allows optimal operation of the electrical purificationapparatus, without encountering leakage within the apparatus, whilemaintaining a large surface area of membrane that may be used in theprocess.

Sealing may be accomplished by any suitable means for ensuring matingbetween the membranes so as to provide the desired fluid flow paththrough compartments defined by the membranes. For example, sealing maybe accomplished by adhesives, thermal bonding by laser or ultrasonicwelding, for example, or by mating or interlocking, for example, usingmale and female features on adjacent membranes and/or spacers. Incertain examples, to construct a membrane cell stack, multiple spacerassemblies are constructed and are bonded or secured together withadhesives applied at portions of the periphery of the spacer assemblies.Spacers are positioned between each of the spacer assemblies securedtogether. In certain examples, the spacer assemblies may be secured toone another at a portion of the periphery of each of the spacerassemblies to provide a plurality of compartments having at least twofluid flow paths. For example, the spacer assemblies may be secured toone another to provide a first compartment having a fluid flow path in afirst direction and a second compartment having a fluid flow path in asecond direction. In place of adhesives, thermal bonding or mechanicalinterlocking features may be used to provide the compartments.

In some embodiments of the disclosure a method for preparing a cellstack for an electrical purification apparatus comprises formingcompartments. A first compartment may be formed by securing ion exchangemembranes to one another to provide a first spacer assembly having afirst spacer disposed between the ion exchange membranes. For example, afirst cation exchange membrane may be secured to a first anion exchangemembrane at a first portion of a periphery of the first cation exchangemembrane and the first anion exchange membrane to provide a first spacerassembly having a first spacer disposed between the first cationexchange membrane and the first anion exchange membrane.

A second compartment may be formed by securing ion exchange membranes toone another to provide a second spacer assembly having a second spacerdisposed between the ion exchange membranes. For example, a second anionexchange membrane may be secured to a second cation exchange membrane ata first portion of a periphery of the second cation exchange membraneand the second anion exchange membrane to provide a second spacerassembly having a second spacer disposed between the second anionexchange membrane and the second cation exchange membrane.

A third compartment may be formed between the first compartment and thesecond compartment by securing the first spacer assembly to the secondspacer assembly, and by positioning a spacer therebetween. For example,the first spacer assembly may be secured to the second spacer assemblyat a second portion of the periphery of the first cation exchangemembrane and at a portion of the periphery of the second anion exchangemembrane to provide a stack assembly having a spacer disposed betweenthe first spacer assembly and the second spacer assembly.

Each of the first compartment and the second compartment may beconstructed and arranged to provide a direction of fluid flow that isdifferent from the direction of fluid flow in the third compartment. Forexample, the fluid flow in the third compartment may be running in adirection of a 0° axis. The fluid flow in the first compartment may berunning at 30°, and the fluid flow in the second compartment may berunning at the same angle as the first compartment (30°) or at anotherangle, such as 120°. In another example, the fluid flow path in thefirst compartment may be running in a direction of 0°. The fluid flowpath in the third compartment may be running at 60°, and the fluid flowpath in the second compartment may be running at 120°. A fluid flow pathin a fourth compartment may be running at 0°.

The method may further comprise securing the assembled cell stack withina housing.

In accordance with one or more embodiments, an electrochemicalseparation system or electrical purification apparatus may be modular.Each modular unit may generally function as a sub-block of an overallelectrochemical separation system. A modular unit may include anydesired number of cell pairs. In some embodiments, the number of cellpairs per modular unit may depend on the total number of cell pairs andpasses in the separation device. It may also depend on the number ofcell pairs that can be thermally bonded and potted in a frame with anacceptable failure rate when tested for cross-leaks and otherperformance criteria. The number can be based on statistical analysis ofthe manufacturing process and can be increased as process controlsimprove. In some non-limiting embodiments, a modular unit may includeabout 50 cell pairs. Modular units may be individually assembled andquality control tested, such as for leakage, separation performance andpressure drop prior to being incorporated into a larger system. In someembodiments, a cell stack may be mounted in a frame as a modular unitthat can be tested independently. A plurality of modular units can thenbe assembled together to provide an overall intended number of cellpairs in an electrochemical separation device. In some embodiments, anassembly method may generally involve placing a first modular unit on asecond modular unit, placing a third modular unit on the first andsecond modular units, and repeating to obtain a plurality of modularunits of a desired number. In some embodiments, the assembly orindividual modular units may be inserted into a pressure vessel foroperation. Multi-pass flow configurations may be possible with theplacement of blocking membranes and/or spacers between modular units orwithin modular units. A modular approach may improve manufacturabilityin terms of time and cost savings. Modularity may also facilitate systemmaintenance by allowing for the diagnosis, isolation, removal andreplacement of individual modular units. Individual modular units mayinclude manifolding and flow distribution systems to facilitate anelectrochemical separation process. Individual modular units may be influid communication with one another, as well as with centralmanifolding and other systems associated with an overall electrochemicalseparation process.

The cell stack may be secured within a frame or support structurecomprising an inlet manifold and an outlet manifold to provide a modularunit. This modular unit may then be secured within a housing. Themodular unit may further comprise a bracket assembly or corner supportthat may secure the modular unit to the housing. A second modular unitmay be secured within the housing. One or more additional modular unitsmay also be secured within the housing. In certain embodiments of thedisclosure, a blocking spacer may be positioned between the firstmodular unit and the second modular unit.

A flow redistributor may be present in one or more of the compartmentsof the cell stack. In assembling the cell stack, a first portion of theperiphery of an ion exchange membrane in the cell stack may beconstructed and arranged to interlock with a first portion of aperiphery of an adjacent ion exchange membrane. In certain examples, afirst portion of a periphery of a first spacer in the cell stack may beconstructed and arranged to interlock with a first portion of aperiphery of an adjacent spacer.

In some embodiments of the disclosure, an electrical purificationapparatus comprising a cell stack is provided. The electricalpurification apparatus may comprise a first compartment comprising ionexchange membranes and may be constructed and arranged to provide adirect fluid flow in a first direction between the ion exchangemembranes. The electrical purification apparatus may also comprise asecond compartment comprising ion exchange membranes and may beconstructed and arranged to provide a direct fluid flow in a seconddirection. Each of the first compartment and the second compartment maybe constructed and arranged to provide a predetermined percentage ofsurface area or membrane utilization for fluid contact. In certainembodiments, the membrane utilization that may be achieved is greaterthan 65%. In other embodiments, the membrane utilization that may beachieved is greater than 75%. In certain other embodiments, the membraneutilization that may be achieved may be greater than 85%. The membraneutilization may be at least in part dependent on the methods used tosecure each of the membranes to one another, and the design of thespacer. In order to obtain a predetermined membrane utilization,appropriate securing techniques and components may be selected in orderto achieve a reliable and secure seal that allows optimal operation ofthe electrical purification apparatus, without encountering leakagewithin the apparatus, while maintaining a large surface area of membranethat may be used in the process.

For example an electrical purification apparatus comprising a cell stackmay be provided. The electrical purification apparatus may comprise afirst compartment comprising a first cation exchange membrane and afirst anion exchange membrane, the first compartment constructed andarranged to provide a direct fluid flow in a first direction between thefirst cation exchange membrane and the first anion exchange membrane.The apparatus may also comprise a second compartment comprising thefirst anion exchange membrane and a second cation exchange membrane toprovide a direct fluid flow in a second direction between the firstanion exchange membrane and the second cation exchange membrane. Each ofthe first compartment and the second compartment may be constructed andarranged to provide a predetermined membrane utilization, for example, afluid contact of greater than 85% of the surface area of the firstcation exchange membrane, the first anion exchange membrane and thesecond cation exchange membrane. At least one of the first compartmentand the second compartment may comprise a spacer, which may be ablocking spacer.

The direct fluid flow in the first direction and the second directionmay be selected and provided by the construction and arrangement of thecompartments. Using the first direction of fluid flow as a directionrunning along a 0° axis, the second direction of fluid flow may run atany angle greater than zero degrees and less than 360°. In certainembodiments of the disclosure, the second direction of fluid flow may beat an angle of 90° angle, or perpendicular, to the first direction offluid flow. In other embodiments, the second direction of fluid flow maybe at an 80° angle to the first direction of fluid flow. If additionalion exchange membranes are secured to the cell stack to provideadditional compartments, the direction of fluid flow in these additionalcompartments may be the same or different from the first direction offluid flow and the second direction of fluid flow. In certainembodiments, the direction of fluid flow in each of the compartmentsalternates between a first direction of fluid flow and a seconddirection of fluid flow. For example, the first direction of fluid flowmay run in a direction of 0°. The second direction of fluid flow may runat a 90° angle, and a third direction of fluid flow in a thirdcompartment may run at a direction of 0°.

The electrical purification apparatus comprising a cell stack mayfurther comprise a housing enclosing the cell stack, with at least aportion of a periphery of the cell stack secured to the housing. A framemay be positioned between the housing and the cell stack to providefirst modular unit in the housing. A flow redistributor may be presentin one or more of the compartments of the cell stack. At least one ofthe compartments may be constructed and arranged to provide flowreversal within the compartment.

In some embodiments of the disclosure, a cell stack for an electricalpurification apparatus is provided. The cell stack may provide aplurality of alternating ion depleting and ion concentratingcompartments. Each of the ion depleting compartments may have an inletand an outlet that provides a dilute fluid flow in a first direction.Each of the ion concentrating compartments may have an inlet and anoutlet that provides a concentrated fluid flow in a second directionthat is different from the first direction. A spacer may be positionedin the cell stack. The spacer may provide structure to and define thecompartments and, in certain examples, may assist in directing fluidflow through the compartment. The spacer may be a blocking spacer whichmay be constructed and arrange to redirect at least one of fluid flowand electrical current through the cell stack. As discussed, theblocking spacer may reduce or prevent electrical current inefficienciesin the electrical purification apparatus.

In some embodiments of the disclosure, an electrical purificationapparatus is provided. The apparatus may comprise a cell stackcomprising alternating ion diluting compartments and ion concentratingcompartments. Each of the ion diluting compartments may be constructedand arranged to provide a fluid flow in a first direction. Each of theion concentrating compartments may be constructed and arranged toprovide a fluid flow in a second direction that is different from thefirst direction. The electrical purification apparatus may also comprisea first electrode adjacent an first ion exchange membrane at a first endof the cell stack, and a second electrode adjacent a second ion exchangemembrane at a second end of the cell stack. Each of the first ionexchange membrane and the second ion exchange membrane may be an anionexchange membrane or a cation exchange membrane. For example, the firstion exchange membrane may be an anion exchange membrane, and the secondion exchange membrane may be a cation exchange membrane. The apparatusmay further comprise a blocking spacer positioned in the cell stack andconstructed and arranged to redirect at least one of a dilute fluid flowand a concentrate fluid flow through the electrical purificationapparatus and to prevent a direct current path between the firstelectrode and the second electrode. As discussed above, the blockingspacer may be constructed and arranged to reduce electrical currentinefficiencies in the electrical purification apparatus.

The cell stack for the electrical purification apparatus may be enclosedin a housing with at least a portion of a periphery of the cell stacksecured to the housing. A frame may be positioned between the housingand the cell stack to provide first modular unit in the housing. Asecond modular unit may also be secured within the housing. A blockingspacer may also be positioned between the first modular unit and thesecond modular unit. A flow redistributor may be present in one or moreof the compartments of the cell stack. At least one of the compartmentsmay be constructed and arranged to provide flow reversal within thecompartment. A bracket assembly may be positioned between the frame andthe housing to provide support to the modular unit and to secure themodular unit within the housing.

In certain embodiments of the disclosure, a portion of the periphery ofthe ion exchange membranes or the spacers in the cell stack may betreated or coated with a material so as to provide an enhanced, securebond with the securing material, such as an adhesive, and the componentsof the cell stack. A seal band may be provided on the spacers,membranes, or both to provide a continuous surface upon which adhesivemay be applied to join ion exchange membranes, such as anion and cationexchange membranes. The seal band may also provide support to theperiphery of the membrane. The seal band may prevent or mitigateadhesive wet-through or wicking of the adhesive, thereby allowing lessadhesive used for securing the spacers and membranes together. The sealbands may also contribute to greater membrane utilization based on lessadhesive being used. In certain examples, the seal band may be appliedto the spacer by injection molding, compression molding, coating, or thelike.

FIG. 1 shows a spacer assembly 10 that comprises cation exchangemembrane 100, spacer 104, and anion exchange membrane 102. The spacer104, which may be a screen spacer, may allow for adhesive 106 to beapplied. The membranes may be sealed along two opposite edges byadhesives or by thermal bonding techniques, for example, laser,vibration, or ultrasonic welding. A wide range of adhesives can be usedfor the membrane side seam, including epoxies with aliphatic,cycloaliphatic and aromatic amine curing agents and urethanes, as willbe described in more detail below. When adhesive is being applied toglue line of the membrane cell, it may be beneficial if the adhesiveremains primarily on the predetermined glue line. If viscosity is toolow, the adhesive may run or drip off from the glue line. If theadhesive viscosity is too high, spreading the adhesive may becomedifficult.

If the spacer is a screen, it may be encapsulated within the adhesivewhich also bonds the two adjacent membranes.

FIG. 2 shows spacer assembly 20 comprising cation exchange membrane 200,spacer 204, and anion exchange membrane 202. Spacer 204 separates cationexchange membrane 200 and anion exchange membrane 202, and may definethe flow compartment and enhance mixing and mass transfer as the liquidstream flows from inlet side 208 to outlet side 210.

FIG. 3 shows first spacer assembly 30 and second spacer assembly 32,separated by spacer 304. The two assemblies are bonded together byadhesives 306 applied along two parallel edges that are perpendicular tothe edges already sealed in the assemblies. Spacer 304 sandwichedbetween the two assemblies defines a flow channel for a second streamthat is perpendicular in direction to the streams flowing through thetwo assemblies, as shown by the arrows.

The resulting membrane cell stack when compressed is shown in FIG. 4. Asshown, the first spacer assembly 40 and the second spacer assembly 42are secured to one another, having spacer 404 positioned between the twospacer assemblies. The flow path through each of the spacer assemblies40 and 42 may go in a first direction, while the flow path through thecompartment defined between the two spacer assemblies may go in a seconddirection, as indicated by the arrows in FIG. 4.

The fluid flow in the first direction may be a diluting stream and thefluid flow in the second direction may be a concentrating stream. Incertain embodiments, the fluid flow in the first direction may beconverted to a concentrating stream and the fluid flow in the seconddirection may be converted to a diluting stream with the use of polarityreversal where the applied electrical field is reversed thus reversingthe stream function.

Multiple spacer assemblies separated by spacers may be secured togetherto form a stack of cell pairs, or a membrane cell stack.

The electrical purification apparatus of the present disclosure mayfurther comprise a housing that encloses the cell stack. At least aportion of the periphery of the cell stack may be secured to thehousing. A frame or support structure may be positioned between thehousing and the cell stack to provide additional support to the cellstack. The frame may also comprise inlet manifolds and outlet manifoldsthat allow the flow of liquid in and out of the cell stack. The frameand the cell stack together may provide an electrical purificationapparatus modular unit. The electrical purification apparatus mayfurther comprise a second modular unit secured within the housing. Aspacer, for example, a blocking spacer, may be positioned between thefirst modular unit and the second modular unit. A first electrode may bepositioned at an end of the first modular unit that is opposite an endin communication with the second modular unit. A second electrode may bepositioned at an end of the second modular unit that is opposite an endin communication with the first modular unit.

A bracket assembly may be positioned between the frame and the housingof the first modular unit, the second modular unit, or both. The bracketassembly may provide support to the modular units, and provide for asecure attachment to the housing.

In one embodiment of the disclosure, the electrical purificationapparatus may be assembled by positioning a membrane cell stack into ahousing or vessel. Endplates may be provided at each end of the cellstack. Adhesive may be applied to seal at least a portion of theperiphery of the cell stack to the inside wall of the housing.

FIG. 5 shows one embodiment of cell stack 516 is enclosed by housing518. Endplates 512 are drawn together with tie-bars 514. Tie-bars 514are isolated from the fluid streams by non-metallic sleeves. Anon-metallic endblock 520 may be inserted between the cell stack 516 andendplate 512 at each end if endplates 512 are metallic. Endblocks 520support the electrodes and isolate the liquid streams from theendplates. The ends of the tie-bar sleeves are sealed against endblocks520 by O-rings. Alternatively, endplate 520 may be non-metallic, and aseparate endblock may then not be necessary. As shown in FIG. 5,endplates 520 may be attached by bolts or threaded rod 522 and nuts 524.As shown in FIG. 6, endplates 620 may be attached by flanges 649. Asshown in FIG. 7, endplates 720 may be attached by clamps 728, such as byVictaulic® type clamps.

In some embodiments of the disclosure, the tie-bars may be locatedoutside the housing. In some other embodiments of the disclosure, theendplates may be secured in the housing by segmented or snap ringsinserted into grooves at the ends of the housing. The endplates may alsobe bonded to the housing by adhesives.

A metallic endplate may be fabricated, for example, by machining orcasting. A non-metallic endblock or endplate may be fabricated, forexample, by machining a block of plastic or by injection molding.

Once the stack is positioned in the housing and the endblocks/endplatesare secured to the housing, adhesive may be applied to seal the stack tothe housing and to isolate the inlet and outlet manifolds for the twostreams from each other. The housing is first oriented with thelongitudinal axis horizontal.

As discussed in further detail below, adhesive properties for securingthe membrane stack within the housing may be different from the adhesiveproperties for securing membranes to one another to form a cell stack.For securing a membrane stack in a housing, the adhesive viscosity mustbe low. The acceptable viscosity could be achieved by adding reactivediluents into the mixed adhesive. The primary function of a diluent isto reduce its viscosity to either make it easier to compound, or toimprove application properties. Lower viscosity may also be important inachieving a suitable adhesive in that it allows greater penetration intoa porous substrate and allows for wetting of non-porous surfaces. Thediluent could be diglycidyl ether, diglycidyl phenyl diglycidyl etherand others.

The membrane cells flow compartments may be about 0.33 mm to 0.46 mmthick and, in certain examples, the pot may be air void free. The potelastomer (adhesive) used to secure the cell stack to the housing shouldbe more rigid than the side seam used to secure membranes to oneanother; this may be because the pot must have enough mechanicalstrength to withstand the weight of a membrane stack. In certainembodiments, it may be desirable if the pot did not deform under feedflow pressure.

The housing is first oriented with the longitudinal axis horizontal.FIG. 8 shows one method of applying adhesive 806 to secure cell stack816 within housing 818. Housing 818 may be rotated so that a peripheryof cell stack 816, in this embodiment, corner 830, is at the bottom. Lowviscosity adhesive 806 is injected into housing 818 and allowed to poolat the bottom. Injections ports may be placed that coincide with aperiphery of cell stack 816, which can be incorporated into housing 818to facilitate injection of adhesive 806 into housing 818 to seal corners830 of cell stack 816 to housing 818. After adhesive 806 sets, housing818 may be rotated 90° until the next corner is at the bottom. Theadhesive process is repeated until all desired peripheries of cell stack816 have been sealed or secured. Surface preparation to improve thesealing of the housing to the stack periphery may include techniquesthat may disrupt the surface and increase the surface area to enhanceadhesive bonding. For example, the surface preparation may comprisechemical, mechanical, electrical, or thermal surface preparation, andcombinations thereof. This may include chemical etching or mechanicalroughing, for example.

The housing may be fabricated, by extrusion, for example, to provide ageometry that assists in securing the cell stack to the housing. Forexample, one or more troughs may be produced in the housing so that theadhesive may be contained in a defined area to receive a periphery ofthe cell stack. As shown in FIG. 9, housing 918 is provided that hasscalloped troughs 932 to provide a reservoir for adhesive 906 to beplaced.

In another embodiment of the disclosure, a method of applying adhesiveis provided that comprises slowly rotating the housing in one directionwhile a controlled quantity of adhesive is injected into the housing.The adhesive continuously flows towards the lowest point and formssuccessive thin layers that may set to form a seal ring around insidewall of the housing. The thickness of the ring can be increased byfurther addition of adhesive.

In another embodiment of the disclosure a method of applying adhesive isprovided that comprises rapidly rotating the housing in one directionwhile a controlled quantity of adhesive is injected into the housing atone or more points. The adhesive may be forced against the inside wallof the housing by centrifugal force and may forms a seal ring as itsets.

The embodiments of the disclosure that provide a method comprisingrotating a housing 1018 in one direction while injecting a controlledamount of adhesive 1006 to the housing are shown in FIG. 10.

In another embodiment of the disclosure, an electrical purificationapparatus may be assembled by sealing a portion of the periphery of thecell stack with adhesive with the use of a mold. The cell stack may beinserted into a housing, and then compressed with endplates at each endof the cell stack. Adhesive may then be applied to seal a periphery ofthe cell stack to the inside wall of the housing.

As shown in FIG. 11, a periphery of a cell stack, in this example,corner 1130 of cell stack 1116, may be inserted into mold 1134. A lowviscosity adhesive 1106 may be poured into mold 1134 and allowed to set.The stack is then rotated to seal other portions of the periphery asshown in FIG. 12, wherein adhesive 1206 is shown at each corner 1230 ofcell stack 1216. In certain examples, the mold is fabricated from amaterial that the adhesive may not adhere to.

As shown in FIG. 13, cell stack 1316 with all four corners sealed isinserted into housing 1318 with gap 1338 between the adhesive 1306 andinner wall 1336 of housing 1318. Gap 1338 is filled with additionaladhesives to seal cell stack 1316 to housing 1318 and prevent cross-leakbetween the flow manifolds.

In another embodiment illustrated in FIG. 14, membrane cell stack 1416with bracket assembly or corner supports 1440 which may be fabricated byextrusion or injection molding, for example, are used as a mold forpotting and sealing the corners of cell stack 1416. The corner supports1440 (and 1540) then serve as anchors to attach the stack to shell 1542,as shown in FIG. 15. Methods that may be used to secure the cornersupports to the shell include plastic joining techniques such asultrasonic welding. Shell 1542 (and 1642) is in turn inserted intohousing 1618 as shown in FIG. 16, thus eliminating the need to pot thestack assembly directly to the outer housing. A bracket assembly orcorner support may also be used to secure a modular unit to a housing.

In certain embodiments of the disclosure, an electrical purificationapparatus is provided that reduces or prevents inefficiencies resultingfrom greater electrical power consumption. The electrical purificationapparatus of the present disclosure may provide for a multiple pass flowconfiguration to reduce or prevent current inefficiencies. The multiplepass flow configuration may reduce the bypass of current through theflow manifolds, or leakage of current, by eliminating or reducing thedirect current path between the anode and the cathode of the electricalpurification apparatus. As shown in FIG. 17, electrical purificationapparatus 50 is provided comprising cathode 1744 and anode 1746. Aplurality of alternating anion exchange membranes 1748 and cationexchange membranes 1750 reside between cathode 1744 and anode 1746 toprovide a series of alternating ion diluting compartments 1752 and ionconcentrating compartments 1754. Blocking spacer 1756 may be positionedwithin one or more of ion diluting compartments 1752 and ionconcentrating compartments 1754 to redirect fluid flow and current flowthrough electrical purification apparatus 50, as shown by the arrows inFIG. 17.

FIG. 18 shows an example of a spacer that may be used as a blockingspacer in an electrical purification apparatus. The spacer may comprisescreen portion 1858, solid portion 1860, and sealing band 1862. Sealingband 1862 may be bonded to the adjacent membranes by adhesives, as shownin FIG. 19. The sealing bands may improve the sealing between membranesand spacer by providing a flat surface for bonding. In certain examples,the spacer may be fabricated by injection molding, machining, thermalcompression, or rapid prototyping.

A molded spacer may be of sufficient thickness so that the screenportion may be molded. The thickness may be larger than that of a screenspacer. As a result the inter-membrane distance for the blockingcompartment may be larger than that in the adjacent compartments,resulting in a higher electrical resistance which may be acceptablesince the number of blocking spacers is limited.

The edge of the spacer at the solid portion may be secured and sealed tothe inside wall of a housing. Solid portion 1860 of the spacer may besufficiently rigid to withstand the pressure differential on the twosides. Structural features such as ribs may be added to the solidportion to increase the stiffness of the material.

As shown in FIG. 19, first spacer assembly 1964 and second spacerassembly 1966 are provided. Blocking spacer 1956 is positioned betweenfirst spacer assembly 1964 and second spacer assembly 1966.

FIG. 20 shows an embodiment of an electrical purification apparatus ofthe present disclosure comprising a three-pass cross-flowelectrodialysis device. Cell stack 2016 is secured within housing 2018.Blocking spacers 2056 are positioned within cell stack 2016 to redirectflow of fluid and current within the electrodialysis device, as shownwith the arrows in FIG. 20.

In another embodiment, a portion of the periphery of the cell stack anda periphery of the blocking spacers are secured with adhesive to theinside surface of the housing.

As shown in FIG. 21, blocking spacer 2156 is provide with circular rim2168 which forms a trough for adhesive 2106 when spacer 2156 is insertedinto a housing. The device may then be assembled as shown in FIG. 22 byinserting a plurality of cell pairs 2216 and blocking spacer 2256 orspacers into housing 2218 and then compressing this assembly withendplates and/or endblocks at both ends. Adhesive 2206 may be appliedsuccessively to a portion of the periphery of the stack by potting.Housing 2318 is then oriented with the axis vertical as shown in FIG.23A, with rims 2368 ready to receive adhesive. As shown in FIG. 23B,adhesive 2306 is applied to the troughs formed by rims 2368 on blockingspacers 2356 to seal the spacers to housing 2318. The adhesive can beinjected through small tubes or catheters inserted through the endplateand/or endblock, for example.

In certain embodiments an additional component, such as a gasket oro-ring, may be used, and positioned around the blocking spacer to assistin containing the liquid adhesive used to secure the spacer to thehousing. In this embodiment, the adhesive, once it has cured, may be theprimary seal. In another embodiment, the additional component such as agasket or o-ring is designed to be the only seal between the blockingspacer and the housing and only adhesive 2206 located at a portion ofthe periphery of the cell stack may be used (see FIG. 22). This maysimplify modular unit assembly by reducing or eliminating the need toseal the rim of the blocking spacer to the housing with an adhesivematerial.

In another embodiment, stacks of cell pairs with dilute and concentratecompartments in single pass flow configurations are first sealed insections of cylindrical housings to form modular units. The units maythen be joined together with blocking spacers in between to formmultiple pass configurations. An advantage of this approach may be thatthe stacks may be sealed to the housing sections using adhesives only ata portion of the periphery, such as the corners. The blocking spacers donot have to be sealed to the inside wall of the housing; they areinstead positioned between the modular units and sealed between theends.

FIG. 24A shows, for example, a first modular unit 2470 and secondmodular unit 2472 with flanges 2474 at the ends and blocking spacer 2456positioned in between. In FIG. 24B, first modular unit 2470 and secondmodular unit 2472 are secured to one another. Flanges 2474 of firstmodular unit 2470 and second modular unit 2472 may be secured together.In certain examples, flanges 2474 of first modular unit 2470 and secondmodular unit 2472 may be bolted together.

FIG. 25 shows another embodiment of a blocking spacer having screenportion 2558, solid portion 2560, and sealing band 2562. The blockingspacer may be molded with circular frame 2576 that is sealed between theflanges with adhesives or gaskets. Alternatively the frame can be moldedof a thermoplastic material so that adhesives or gaskets are notnecessary. Other methods for fabricating blocking spacers will beapparent to those skilled in the art.

Alternatively, the modular units can be connected together with clamps,tie-bars or other securing techniques. The design of the blocking spacermay be modified accordingly to accommodate the selected securingtechnique.

In some embodiments of the disclosure, a method for preparing a cellstack is provided. A first spacer assembly may be prepared by securing afirst ion exchange membrane to a second ion exchange membrane at a firstportion of the periphery. At a second portion of the first ion exchangemembrane and the second ion exchange membrane, the periphery may befolded to provide end folds. A spacer may be provided between the firstion exchange membrane and the second ion exchange membrane. A secondspacer assembly may be prepared similarly. The end folds of the firstspacer assembly may be aligned with the end folds of the second spacerassembly so that the end folds of the second ion exchange membrane aresecured to the end folds of an ion exchange membrane of the secondspacer assembly. The end folds may then be collapsed, and a spacer maybe positioned between the spacer assemblies. As the spacer assembliesare compressed, compartments are created to provide for a fluid flowstream between the spacer assemblies in a direction different than thefluid flow stream within each of the first spacer assembly and thesecond spacer assembly.

As shown in FIG. 26, a first spacer assembly may be prepared by securingfirst anion exchange membrane 2602 to first cation exchange membrane2600 at a first portion of the periphery. In this example, the firstportion of the periphery is secured by thermal bond 2678. At a secondportion of the first anion exchange membrane and the first cationexchange membrane, the periphery may be folded to provide end folds2680. Spacer 2604 may be provided between first anion exchange membrane2602 and first cation exchange membrane 2600.

A second spacer assembly may be prepared similarly. As shown in FIG. 27,end folds 2780 of the first spacer assembly may be aligned and mayoverlap with end folds 2784 of the second spacer assembly so that theend folds of the first cation exchange membrane is secured to the endfolds of the anion exchange membrane of the second spacer assembly. Theoverlapping portion of the end folds may secured by thermal bonding,adhesives, or mechanical techniques. As shown in FIG. 28, the end foldsmay then be collapsed, and spacer 2804 may be positioned between thespacer assemblies. As the spacer assemblies are compressed, compartmentsare created to provide for fluid flow stream 2986 between the spacerassemblies in a direction different than fluid flow stream 2988 withineach of the first spacer assembly and second spacer assembly as shown inFIG. 29 by the arrows.

By using thermal bonding techniques to prepare the spacer assemblies andthe resultant cell stack, a process is provided that may allow for easeof assembly, and may provide for faster overall assembly time of anelectrical purification apparatus. The narrow thermal seals provide forlarger flow channels that may result in higher membrane utilization,which may increase the efficiency of the overall electrical purificationapparatus. In certain embodiments utilizing thermal bonding, additionalre-enforcement strips of a polymeric material, for example,polypropylene or polyethylene, may be used to strengthen the thermalbonding areas and to provide a more robust seal. By thermal bonding themembranes prior to collapsing and compressing the membranes, may alsoassist in ease of assembly, as there may be more room for theappropriate bonding equipment and devices to assist in the bondingprocess. The thermal bonding techniques may also prevent leaks in themembrane stack. This process may also reduce the compressive force tomembrane spacers to maintain the cell stack integrity, resulting in alower pressure drop through the modular unit.

In some embodiments, adhesives may be used to secure the ion exchangemembranes and spacers in a cell stack. Adhesives that may be useful inpreparing a cell stack may have particular characteristics or propertiesthat allow for a suitable seal of the components of the cell stack andto secure the cell stack within an electrical purification apparatushousing. These properties may include the adhesive's viscosity, geltime, cure temperature and elastomeric properties. By modifying theproperties of the adhesive, it has been found that the bond strengthbetween the membrane stack and the housing may be enhanced, and theleakages within the electrical purification apparatus may be reduced oreliminated.

In some cases epoxy or epoxy-based materials or polyurethane orpolyurethane-based materials may be used. This may be due to theirthermal, mechanical, and chemical properties that may allow them toprovide suitable sealing of membranes to one another, and to cell stacksto housings.

The epoxy or epoxy-based material may comprise a resin and a curingagent. To provide suitable sealing to the membranes or to the housing,the resin may require crosslinking. This crosslinking may be achieved bychemically reacting the resin with a suitable curing agent. The curingagent may be selected from the group consisting of aliphatic amines,amindoamine, cycloaliphatic amine, and aromatic amine. The curing agentsmay provide particular properties to the adhesive, including, but notlimited to, viscosity, pot life, curing time, penetration, wettingability, mechanical strength, and chemical resistance after curing.

The polyurethane or polyurethane-based materials may be produced by thepoly addition reaction of an isocyanine with a polyalcohol (polyol) inthe presence of a catalyst. The reaction may provide a polymercontaining urethane linkage, —RNHCOOR′—.

When an adhesive is desired that is suitable to use to secure membranesto one another, in some embodiments, it may be desirable that theadhesive remain to a certain extent on a predetermined glue line or sealband. If, for example, the viscosity of the adhesive is too low, theadhesive may run or drip off from the glue line or seal band. If theadhesive viscosity is too viscous, spreading of the adhesive may becometoo difficult.

In certain embodiments, it may be desirable to use an adhesive that hasa similar thermal expansion as the membrane to secure the membranes toone another. This may prevent or reduce cracks or wrinkles at themembrane-adhesive interface. In order to determine a suitable adhesivefor electrical purification apparatus applications, the concentration ofamine curing agent may be altered. For example, aliphatic amine has astraight carbon backbone chain, which may provide a high degree offlexibility for thermal expansion. Use of this type of curing agent mayallow the side seam to expand along with the membrane. Cycloaliphaticand aromatic amine curing agents have aromatic rings in their back bonechain, which may provide rigid elastomer properties.

In certain embodiments of this disclosure, adhesives that may be used tosecure membranes to one another may have a viscosity in a range fromabout 1000 to about 45,000 cps at ambient temperature may be used. Thismay provide a gel time in a range from about 15 minutes to about 30minutes. The adhesive may have a shore D hardness in a range from about30 to about 70 at ambient temperature.

The adhesive may be applied by any suitable means, and it may be appliedby an automated or manual procedure. The seam that the adhesive createsmay have a width in a range of about 0.25 inches to about 1.5 inches,and a glue thickness in a range of about 20 mils to about 50 mils. Theadhesive may be cured by using ultraviolet light, ambient temperature,accelerated temperature, or the like.

Adhesives that may be use for securing a membrane cell stack to ahousing may have a low viscosity, which may be achieved by addingreactive diluents into the mixed adhesive. By adding a diluent, a lowerviscosity adhesive may be obtained, and may allow for easier applicationof the adhesive. The lower viscosity may also provide a greaterpenetration into a porous substrate and better wetting on a non-poroussurface. In certain examples, the diluent may be selected from the groupconsisting of diglycidyl ether, diglycidyl phenyl diglycidyl ether, andcombinations thereof.

The adhesive used to secure the cell stack to the housing may be morerigid than the adhesive used to secure the membranes to one another. Theadhesive used to secure the cell stack to the housing may be formulatedto have enough mechanical strength to withstand the weight of themembrane cell stack, and may not deform under flow pressure.

In certain embodiments of this disclosure, the adhesive used to securethe cell stack to the housing may have a viscosity in the range fromabout 300 cps to 2000 cps at ambient temperature. Gel time of theadhesive may range from about 30 minutes to about 60 minutes. Theadhesive may have a shore D in a range of about 45 to 80 at ambienttemperature.

The housing in which the membrane cell stack is positioned and securedto provide the electrochemical purification apparatus may be made of anysuitable material to allow for fluid flow and current flow within theapparatus, and to retain fluid and current within it. For example, thehousing or housing may be constructed of polysulfone, polyvinylchloride,polycarbonate or epoxy impregnated fiberglass. The materials used forthe housing may produced from an extrusion process, injection molding,or other process that typically provides a dense structure with agenerally smooth interior. To enhance the adhesive bond between thehousing and the membrane cell stack, which may fail due to forces ofcontinuous fluid flow, a portion of the interior surface of the housingwhere the membrane cell stack may be secured is treated or modified.Surface preparation to improve the sealing of the housing to the stackperiphery may include techniques that may disrupt the surface andincrease the surface area to enhance adhesive bonding. For example, thesurface preparation may comprise chemical, mechanical, electrical, orthermal surface preparation, and combinations thereof. This may includechemical etching or mechanical roughing, for example.

In certain embodiments, adhesive injection ports in the housing are usedto aid in the delivery of adhesive to the desired areas in the housingin order to secure the membrane cell stack to the housing. One or moreadhesive injection ports may be used to introduce the adhesive to thehousing. More than one adhesive port may be utilized at each securingpoint in the housing. In certain embodiments, three adhesive injectionports may be provided in a particular arrangement to distribute adhesivein the appropriate manner to the securing point. The adhesive injectionports may be positioned in a straight line, or may be scattered in aparticular design or pattern to achieve the desired adhesive delivery.In examples where a low viscosity adhesive is used, it may penetrateinto the channels of the membrane cell stack to enhance the bond betweenthe membrane cell stack and the housing. By injecting adhesive in thismanner, the amount of adhesive that is being used and the exothermicheat generated by the adhesive may be monitored.

In certain embodiments of this disclosure, the membranes may be securedto one another and to spacers within the membrane cell stack bymechanical sealing techniques. The sealing may be accomplished by theformation of ridges or grooves on at least one of the membranes and thespacers used in the electrical purification apparatus. The ridges orgrooves on a first membrane or spacer may mate with the ridges orgrooves on a second membrane or spacer. The ridges or groove on a firstmembrane or spacer may interlock with the ridges or grooves on a secondmembrane or spacer. For example, the ridges or grooves on a firstmembrane or spacer may be male ridges or fittings that mate with theridges or groves on the second membrane or spacer, which may be femaleridges or fittings. An ion exchange membrane such as a cation exchangemembrane or an anion exchange membrane may be positioned and securedbetween the first spacer and the second spacer. In certain embodiments,once a series of spacers and ion exchange membranes has been assembledto form a plurality of concentrate and dilute flow compartments, thecompartments may be filled with a resin, in the form of a resin slurryor resin suspension, for example.

FIG. 30 shows an example of an injection molded dilute spacer 3004 withgrooves 3090 for mating seals on both faces of spacer 3004. One end ofeach flow compartment 3092 is closed off with the exception of openings3094 that retain ion exchange resin beads, but may allow fluid flow. Theother end 3096 of spacer 3004 may be open for resin filling. Slots 3098may be present at the end to accommodate resin retaining plates. Aconcentrate spacer may be constructed in the same manner. In certainexamples, the concentrate spacer may be thinner than the dilute spacerbecause in certain embodiments, the concentrate flow may be lower thanthe flow through the dilute compartments.

FIG. 31 shows a cross-sectional view through a stack of spacers 3104 andcation exchange membrane 3100 and anion exchange membranes 3102 prior toassembly. Female features 3101 on first spacer 3104 a may be mated withthe male features 3103 on second spacer 3104 b. Male features 3103 onsecond spacer 3104 b may also be mated with the female features 3101 onthird spacer 3104 c.

To enhance the transfer of ions through the resin beads and themembranes, it may be desirable to have the resin beads tightly packed.This may be particularly advantageous in the dilute compartments inultrapure water applications. It has been found that there are manypossible ways to increase the packing density. For example, resins maybe soaked in a concentrated salt solution, such as sodium chloride, andthen slurried into the compartments. During operation of the electricalpurification apparatus, the resins in the dilute compartments may swellas the dilute stream is deionized. The resins may also be soaked in aconcentrated salt solution, such as sodium chloride, and then dried. Theresins may then be suspended in an air stream and then blown into thecompartments. During operation, the resins in both the dilute andconcentrate compartments may swell as they are exposed to fluid, and theresins in the dilute compartments will swell further as the dilutestream is deionized. In another example, the concentrate compartmentsmay be filled before the dilute compartments. The membranes will beallowed to bulge into the dilute compartments, and then the dilutecompartments may be filled. Expansion of the resins in the dilutecompartment during operation may be constrained by the resins packedinto the concentrate, thereby increasing the packing density.

FIG. 32 shows a section view of a part of an assembled stack of spacers3204, including 3204 a, 3204 b, and 3204 c, and membranes and a detailedview of the mechanical seals interlocking. As shown in the detailedview, compartments 3292 may be filled with resins once the stack withthe desired number of cell pairs is assembled. A slurry of resin in afluid is pumped into the compartments. The resins may be retained inopenings 3294 at the bottom of the compartments while the resin carrierfluid flows through. When the compartments are full, slotted plates areslid into place to retain resin in the compartments. The stack may thenbe rotated 90° and the dilute compartments may be filled with resin in asimilar manner.

FIG. 33 shows a part of a membrane cell stack 3305 with resin retainingplates 3307 in place. Membrane cell stack 3305 may be secured in ahousing at particular points along the periphery of cell stack 3305. Forexample, the cell stack may be secured at one or more corners 3330 ofcell stack 3305.

In another embodiment, the membranes may be sealed to the spacers withovermolded thermoplastic rubber (TPR) seals. After a stack of spacersand membranes is assembled and compressed, the concentrate and diluteflow compartments are filled with resins. FIG. 34 shows dilute spacer3404 with rim 3407 and overmolded seal 3409. The overmolded seal may bepresent on both faces of the spacer. The concentrate spacer may beconstructed similarly. In certain examples, the concentrate spacer maybe constructed to be thinner than the dilute spacer, and may notcomprise overmolded seals.

FIG. 35 is a section view through part of a stack of spacers andmembranes, including concentrate spacer 3511 and dilute spacer 3513.Openings 3594 retain resin within compartments 3592, and openings orslots 3598 at the opposite end of compartments 3592 allow for resinfilling. In this particular embodiment, circular rims 3507 are shown,but other rim shapes can be used, such as rectangular, square, orpolygonal, so long as the resultant cell stack may be adequately securedto the housing. In some embodiments, rims 3507 may eliminate the needfor a housing. Radial overmolded seals 3509 may separate the dilute andconcentrate inlet/outlet manifolds and therefore eliminate therequirement for corner securing or potting. Before adding resin to thestack, the stack may be compressed to seal the membranes and spacerstogether. This may be accomplished with, for example, temporary tie barsor clamps.

FIG. 36 is a section view showing resin retaining plates 3607 in placeafter resin filling dilute compartments 3615.

In certain embodiments, the sealing by overmolded seals and the matingby male features and female features may be used together to provide asecured membrane cell stack. The membranes may be sealed to the spacerswith male and female features, while radial overmolded seals and theseals in the rim may seal the dilute spacers to the concentrate spacers.In this embodiment, it may not be necessary to use a housing or cornerseals to seal the cell stack to a housing.

In certain embodiments, an injection molded spacer 3704 is provided thatincorporates screen area 3725 as shown in FIG. 37. This Figure shows afluid flow direction 3727. Openings are provided in two opposite edges3729 and 3731. The openings may be formed by wires that are retractedprior to ejection of the part from the mold.

FIGS. 38A and 38B show details of openings, for example at 3833, in edge3829 as discussed regarding FIG. 37. FIGS. 38A and 38B also show malefeatures 3803 which may interlock with female features 3801.

A dashed parting line is shown in FIG. 38B. The spacer may be moldedwith one set of strands above parting line 3835 of the mold and one setof strands below parting line 3835. The strands of the screen spacer asshown in FIG. 38B have semi-circular cross-sections and the two sets ofstrands are oriented perpendicular to each other. The cross-sectionalshape, orientation and frequency of the strands may be varied to promotefluid mixing and/or reduce a pressure drop. Ribs or baffles may bemolded into the spacer to form flow channels and improve flowdistribution.

In certain embodiments, the male and female features are molded on thetop and bottom respectively of the edges that contain inlet and outletopenings 3833.

The selection of material for the spacer may depend on the ability forit to be molded with thin walls and small dimensions, for example, onthe order of about 0.060 inches (1.5 mm) or less. The material may alsohave the ability to be molded with small holes, preferably on the orderof about 0.030 inches (0.75 mm) or less. The material may have asuitable elasticity to allow appropriate interlocking of the male andfemale features, and may have chemical compatibility with the fluid tobe purified.

FIG. 39 shows a portion of a stack of spacers and membranes. As shown,male features 3903 interlock with female features 3901. Similarly, inFIG. 40, male features 4003 interlock with female features 4001. Cationexchange membranes 4000 and anion exchange membranes 4002 are securedbetween the spacers. Spacers for a first stream 4037 seal the edges ofthe membranes bound for the second stream, while spacers for the secondstream 4039 seal the edges of the membranes bound for the first stream.

In certain embodiments of the disclosure the flow within a compartmentmay be adjusted, redistributed, or redirected to provide greater contactof the fluid with the membrane surfaces within the compartment. Thecompartment may be constructed and arranged to redistribute fluid flowwithin the compartment. The compartment may have obstructions,projections, protrusions, flanges, or baffles that may provide astructure to redistribute the flow through the compartment. Theobstructions, projections, protrusions, flanges, or baffles may beformed as part of ion exchange membranes, the spacer, or may be anadditional separate structure that is provided within the compartment.The obstructions, projections, protrusions, flanges, or baffles may beformed by providing an extension from an adhesive that may secure theion exchange membranes to one another. The spacer may be impregnatedwith thermoplastic rubber to form protrusions that may be bonded withadhesive to adjacent membranes. The thermoplastic rubber may be appliedto the spacer using processes such as thermo-compression or rotaryscreen printing. The compartments may or may not contain ion exchangeresin.

As shown in FIG. 41, first ion exchange membrane 4151 and second ionexchange membrane 4153 are shown with first spacer 4155 and a secondspacer 4157 positioned adjacent them. First stream 4159 is shown asflowing parallel to the flow of second stream 4161, due to second spacer4157 having baffles that redistribute the flow from inlet 4163 of spacer4157, around first baffle 4165 and around second baffle 4167, andthrough outlet 4169.

As shown in FIG. 42, first ion exchange membrane 4251 and second ionexchange membrane 4253 are shown with first spacer 4255 and secondspacer 4257 positioned adjacent them. First stream 4259 is shown asflowing perpendicular to the flow of second stream 4261, due to secondspacer 4257 having baffles that redistribute the flow from inlet 4263 ofspacer 4257, around first baffle 4265 and around second baffle 4267 andthrough outlet 4269.

FIGS. 43 and 44 show additional embodiments with the compartments forthe two streams formed by injection molded spacers. In FIG. 43, the flowpath for second stream 4361 may be co-current or counter-current tofirst stream 4359. In FIG. 44, the flow path for second stream 4461 maybe perpendicular to first stream 4459. Selected solid portions of thespacers may be bonded to adjacent membranes with adhesives.Alternatively, the membranes may be thermally bonded to the spacers,such as by ultrasonic, vibration, or laser welding. As shown in theseFigures, the dotted arrows indicate the flow in the inlet and outletmanifolds for the second stream. These manifolds are not contingent tothe inlet and the outlet to the flow compartment for the second stream.Therefore, the leakage current down the manifolds between the anode andthe cathode is expected to be reduced.

In some embodiments of the disclosure, a method of providing a source ofpotable water is provided. In certain embodiments, a method offacilitating the production of potable water from seawater is provided.The method may comprise providing an electrical purification apparatuscomprising a cell stack. The method may further comprise fluidlyconnecting a seawater feed stream to an inlet of the electricalpurification apparatus. The method may further comprise fluidlyconnecting an outlet of the electrical purification apparatus to apotable point of use. Seawater or estuary water may have a concentrationof total dissolved solids in a range of about 10,000 to about 45,000ppm. In certain examples, the seawater or estuary water may have aconcentration of total dissolved solids of about 35,000 ppm.

In this embodiment, the cell stack may comprise alternating ion dilutingcompartments and ion concentrating compartments. Each of the iondiluting compartments may be constructed and arranged to provide a fluidflow in a first direction. Each of the ion concentrating compartmentsmay be constructed and arranged to provide a fluid flow in a seconddirection that is different from the first direction, as discussedabove. Further, each of the ion concentrating compartment and the iondiluting compartments may be constructed and arranged to provide apredetermined percentage of surface area or membrane utilization forfluid contact to each of the alternating ion diluting compartments andion depleting compartments. As discussed above, it has been found thatgreater membrane utilization provides greater efficiencies in theoperation of the electrical purification apparatus. In certainembodiments, the membrane utilization that may be achieved is greaterthan 65%. In other embodiments, the membrane utilization that may beachieved is greater than 75%. In certain other embodiments, the membraneutilization that may be achieved may be greater than 85%.

At least one of the ion diluting compartments and ion concentratingcompartments may comprise a spacer. The spacer may be a blocking spacer.This may allow passing of the seawater feed through multiple stages orpasses through the electrical purification apparatus to provide thesource of potable water.

The first direction of fluid flow and the second direction of fluid flowmay be selected and provided by way of the construction and arrangementof the compartments. Using the first direction of fluid flow as adirection running along a 0° axis, the second direction of fluid flowmay run in a direction of any angle greater than zero degrees and lessthan 360°. In certain embodiments of the disclosure, the second fluidflow path may run at a 90° angle, or perpendicular to the first fluidflow path. In other embodiments, the second fluid flow path may run at a180° angle to the first fluid flow path.

The method may further comprise redistributing fluid within at least oneof the alternating ion diluting compartments and ion concentratingcompartments. One or more of the compartments may be constructed andarranged to redistribute or redirect the fluid flow. This may beaccomplished through use of a particular spacer or membrane that definesthe compartment that may provide a configuration to redistribute thefluid flow, as described above.

The electrical purification apparatus may further comprise a housingenclosing the cell stack. At least a portion of the periphery of thecell stack may be secured to the housing. The electrical purificationapparatus may further comprise a frame or support structure positionedbetween the housing and the cell stack. The frame may be adjacent to orconnected to the cell stack to provide a modular unit. The electricalpurification apparatus may further comprise a second modular unit thatmay be secured within the housing. The second modular unit may besecured within the housing such that an ion exchange membrane of thefirst modular unit is adjacent an ion exchange membrane of the secondmodular unit.

The method of providing a source of potable water may compriseredirecting at least one of electrical current and fluid flow betweenthe first modular unit and the second modular unit. This may beaccomplished, for example, by providing a blocking spacer between thefirst modular unit and the second modular unit.

A bracket assembly may be positioned between the frame and the housingto secure the modular unit to the housing.

Other types of feed water comprising different concentrations of totaldissolved solids may be treated or processed using the apparatus andmethods of the present disclosure. For example, brackish water, having atotal dissolved solids content in a range of about 1000 ppm to about10,000 ppm may be treated to produce potable water. Brine, having atotal dissolved solids content in a range of about 50,000 ppm to about150,000 ppm may be treated to produce potable water. In someembodiments, brine, having a total dissolved solids content in a rangeof about 50,000 ppm to about 150,000 ppm may be treated to produce awater having a lower total dissolved solids content for purposes ofdisposal, for example, to a body of water, such as an ocean.

While exemplary embodiments of the disclosure have been disclosed manymodifications, additions, and deletions may be made therein withoutdeparting from the spirit and scope of the disclosure and itsequivalents, as set forth in the following claims.

Those skilled in the art would readily appreciate that the variousparameters and configurations described herein are meant to be exemplaryand that actual parameters and configurations will depend upon thespecific application for which the electrical purification apparatus andmethods of the present disclosure are used. Those skilled in the artwill recognize, or be able to ascertain using no more than routineexperimentation, many equivalents to the specific embodiments describedherein. For example, those skilled in the art may recognize that theapparatus, and components thereof, according to the present disclosuremay further comprise a network of systems or be a component of a waterpurification or treatment system. It is, therefore, to be understoodthat the foregoing embodiments are presented by way of example only andthat, within the scope of the appended claims and equivalents thereto,the disclosed electrical purification apparatus and methods may bepracticed otherwise than as specifically described. The presentapparatus and methods are directed to each individual feature or methoddescribed herein. In addition, any combination of two or more suchfeatures, apparatus or methods, if such features, apparatus or methodsare not mutually inconsistent, is included within the scope of thepresent disclosure.

For example, the housing may be of any suitable geometry such that oneor more membrane cell stacks or modular units may be secured within. Forexample, the housing may be cylindrical, polygonal, square, orrectangular. With regard to the membrane cell stacks and modular units,any suitable geometry is acceptable so long as the cell stack or modularunit may be secured to the housing. For example the membranes or spacersmay be rectangular in shape. In certain embodiments, a housing may notbe required. The geometry of the membranes and spacers may be of anysuitable geometry such that the membranes and spacers may be securedwithin a cell stack. In certain embodiments, a particular number ofcorners or vertices on the cell stack may be desired. For example, threeor more corners or vertices may be desired to secure the cell stack tothe housing. In certain embodiments, the geometry of any of the housing,cell stack, membranes, and spacers may selected to accommodateoperational parameters of the electrical purification apparatus. Forexample, the spacers may be asymmetrical to accommodate differences inflow rates between the dilute and concentrate streams.

Further, it is to be appreciated various alterations, modifications, andimprovements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe disclosure. For example, an existing facility may be modified toutilize or incorporate any one or more aspects of the disclosure. Thus,in some cases, the apparatus and methods may involve connecting orconfiguring an existing facility to comprise an electrical purificationapparatus. Accordingly, the foregoing description and drawings are byway of example only. Further, the depictions in the drawings do notlimit the disclosures to the particularly illustrated representations.

As used herein, the term “plurality” refers to two or more items orcomponents. The terms “comprising,” “including,” “carrying,” “having,”“containing,” and “involving,” whether in the written description or theclaims and the like, are open-ended terms, i.e., to mean “including butnot limited to.” Thus, the use of such terms is meant to encompass theitems listed thereafter, and equivalents thereof, as well as additionalitems. Only the transitional phrases “consisting of” and “consistingessentially of,” are closed or semi-closed transitional phrases,respectively, with respect to the claims. Use of ordinal terms such as“first,” “second,” “third,” and the like in the claims to modify a claimelement does not by itself connote any priority, precedence, or order ofone claim element over another or the temporal order in which acts of amethod are performed, but are used merely as labels to distinguish oneclaim element having a certain name from another element having a samename (but for use of the ordinal term) to distinguish the claimelements.

What is claimed is:
 1. An electrical purification apparatus comprising:a cell stack comprising: a first compartment comprising a first cationexchange membrane, a first anion exchange membrane, and a first spacerpositioned between the first cation exchange membrane and the firstanion exchange membrane, the first spacer sealed along two oppositeedges to the first cation exchange membrane and the first anion exchangemembrane, the first compartment constructed and arranged to provide afluid flow in a first direction between the first cation exchangemembrane and the first anion exchange membrane; and a second compartmentcomprising the first anion exchange membrane, a second cation exchangemembrane, and a second spacer positioned between the first anionexchange membrane and the second cation exchange membrane, the secondspacer sealed along two opposite edges to the first anion exchangemembrane and the second cation exchange membrane, to provide a fluidflow in a second direction between the first anion exchange membrane andthe second cation exchange membrane; a housing enclosing the cell stack;and a frame positioned between the housing and the cell stack to providea first modular unit, the frame comprising inlet and outlet manifolds influid communication with at least one of the first compartment and thesecond compartment, the frame constructed and arranged to provide thefluid flows in the first and second directions and to provide a currentbypass path through the inlet and outlet manifolds having an electricalresistance greater than that of a direct path through the cell stack. 2.The electrical purification apparatus of claim 1, further comprising asecond modular unit secured within the housing.
 3. The electricalpurification apparatus of claim 2, further comprising a blocking spacerpositioned between the first modular unit and the second modular unit.4. The electrical purification apparatus of claim 1, further comprisinga bracket assembly positioned between the frame and the housing.
 5. Theelectrical purification apparatus of claim 1, wherein the firstdirection is perpendicular to the second direction.
 6. The electricalpurification apparatus of claim 1, further comprising a flowredistributor within at least one of the first compartment and thesecond compartment.
 7. The electrical purification apparatus of claim 1,wherein at least one of the first compartment and the second compartmentis constructed and arranged to provide flow reversal within thecompartment.
 8. The electrical purification apparatus of claim 1,wherein at least one of the first spacer and the second spacer is ablocking spacer.
 9. The electrical purification apparatus of claim 8,wherein the blocking spacer is constructed and arranged to redirectelectrical current to the cell stack to improve current efficiency. 10.The electrical purification apparatus of claim 1, wherein the firstspacer further comprises a sealing band, the sealing band bonded to thefirst anion exchange membrane and to the first cation exchange membrane.11. The electrical purification apparatus of claim 1, further comprisinga seam formed by sealing the first spacer along two opposite edges tothe first cation exchange membrane and the first anion exchangemembrane, the seam having a width in a range of about 0.25 inches toabout 1.5 inches.
 12. The electrical purification apparatus of claim 1,further comprising a seam, formed by sealing the first spacer along twoopposite edges to the first cation exchange membrane and the first anionexchange membrane, the seam having a glue thickness in a range of about20 mils to about 50 mils.
 13. The electrical purification apparatus ofclaim 1, wherein each of the first compartment and the secondcompartment is constructed and arranged to provide a fluid contact ofgreater than 85% of the surface area of each of the first cationexchange membrane, the first anion exchange membrane, and the secondcation exchange membrane.
 14. The electrical purification apparatus ofclaim 1, wherein the frame is constructed and arranged such that thecurrent bypass path is more tortuous than a direct path through the cellstack.